Snow is a form of frozen water. It contains many groups of tiny ice particles called snow crystals. These crystals grow from water particles in cold clouds. They usually grow around a piece of dust.
All snow crystals have six sides, but they grow in different shapes. The shape depends mainly on the temperature and water levels in the air. Snow crystals grow in one of two designs -- platelike and columnar. Platelike crystals are flat. They form when the air temperature is about fifteen degrees below zero Celsius. Columnar snow crystals look like sticks of ice. They form when the temperature is about five degrees below zero.
The shape of a snow crystal may change from one form to another as the crystal passes through levels of air with different temperatures. When melting snow crystals or raindrops fall through very cold air, they freeze to form small particles of ice, called sleet. Groups of frozen water droplets are called snow pellets. Under some conditions, these particles may grow larger and form solid pieces of ice, or hail.
Snow contains much less water than rain. About fifteen centimeters of wet snow has as much water as two and one-half centimeters of rain. About seventy-six centimeters of dry snow equals the water in two and one-half centimeters of rain.
Generally, the color of snow and ice appears white. This is because the light we see from the sun is white. Most natural materials take in some sunlight. Sometimes, snow or ice may appear to be blue. The blue light is the product of a long travel path through the snow or ice.
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